Loop lock sewing machine



Feb. 13, 1951 F. PRAVDA LOOP LOCK SEWING MACHINE 2 Sheets-Sheet 1 Filed Jan. 27, 1948 INVENTOR Feb. 13, 1951 PRAVDA v 7 2,541,608

LOOP LOCK SEWI NG MAOHINE Filed Jan. 27, 1948 2 Sheets-Sheet 2 INVENTOR flaw/4 Patented Feb. 13, 1951 UNITED STATES PATENT OFFICE LOOP LOCK SEWING MACHINE Frank Pravda, Plainfield, N. J. Application January 2'7, 1948, Serial No. 4,642

6 Claims. (01. 11232) This invention relates to sewing machines, and is more particularly directed toward sewing machines of the type using waxed or glued threads such as employed in sewing soles on shoes.

Shoe machines of this general type employ two threads; one a machine thread operated by the needle and drawn through a wax container so that waxed thread is applied to the lower side of the work, and the second a waxed bobbin thread which'is applied to the top of the work. In the ordinary procedure the operator passes raw thread from a large spool through a heated wax pot and winds it onto a comparatively small metal bobbin. This bobbin is inserted into a rotary shuttle which is kept hot during the operation of the machine. The amount of thread which can be stored on one of these bobbins is very small, and hence the amount of work which an operator can do with the machine without stopping to replace, reheat and perhaps rewind bobbins is therefore limited. This frequent replacement of bobbins with time consumed in heating them so that they can be used is a considerable handicap to the output of the operator.

The present invention contemplates a sewing machine including a reciprocatable rocker arm containing a thread carrying finger and loop retaining fingers, and a swingable arm containing a loop retaining finger. The rocker arm and swingable arm operate in timed relation from a face cam. The rocker arm thread carrying finger is passed by a sewing position while the machine thread loop is transferred to the loop retaining fingers by the cooperation of the rocker arm loop retaining fingers and the swingable arm loop retaining finger. This loop is retained a suitable time so that the swingable arm loop retaining finger can enter the upper thread loop, which has been passed through the machine thread loop.

by the rocker arm loop carrying finger, and hold said loop until it can be drawn into the material by the machine thread loop which is operated on by the usual tightening mechanism.

Another object of the invention is to provide a sewing machine wherein the thread for the upper part of the work is passed from the large raw thread spool through the wax pot,.around a tension wheel, through a slack take up device and directly to the sewing mechanism.

A further object of the invention is to produce a novel loop locking stitch wherein the upper part of the stitch is heavier forming sort ofa head which is drawn into a hole that is larger at the upper part of the work to receive thehead. .A break in the thread on the upper surface of the work has no weakening effect on the holding strength of said stitch.

A further object of the invention is to provide a means to produce a hole in the material that is larger at the upper part of the work so that the larger portion of the stitch may therein be drawn.

Further objects of my invention will become apparent as the specification of the same pro- 'ceeds.

The accompanying drawings show, for purposes of illustrating the present invention, one of the many embodiments in which the invention may take form, it being understood that the drawings are illustrative of the invention rather than limiting the same.

In these drawings:

Figure 1 is a front View taken in the direction of the arrow of Figure 5 with part of the cover broken away and showing the swingable arm in the raised position and the rocker arm in the left hand position just after the awl has withdrawn from the material.

Figure 2 is a view similar to Figure 1 with the cover removed and. the swingable arm lowered and the rocker arm in the right hand position where it has passed the upper thread loop through the machine thread loop and the latter has been transferred to the rocker arm retaining fingers.

Figure 3 is an elevated view of the slack take up mechanism taken from the left of Figure l as indicated by arrow 3.

Figure 4 is a diagrammatic view illustrating the timing relation of the mechanisms employed.

Figure 5 is a view taken from the right of Figure 2 as indicated by arrow 2 showing the usual horizontal shaft on which the cam is mounted.

Figure 6 is a side View of the needle.

Figure 6a is an enlarged sectional View of the needle taken on the line ara of Figure 6.

Figure 7 is a fragmentary view similar to Figures 1 and 2 showing the free end of the rocker arm in the left hand position, and the free end of the swingable arm in the lowered position as the usual thread tightening means starts into p y- Figure 8 is a sectional view of two pieces of material sewn together by the novel stitch pro duced by the present invention and shows the formation of the stitch within the material.

The face cam l is mounted in the same position, operates on the same horizontal shaft 2, and

is given similar reciprocating rotary motion as the shuttle on the usual machines as will be 'tion'of he stitch.

the roller 25 to the right.

obvious from Figure 5. This face cam contains a horse shoe shaped groove 3, and a roller 4 mounted onthe pin 5 between the ends of the groove.

The rocker arm 6, pivoted at the upper right by means of the stud I, contains a roller 8 that rides in the groove 3 of the face cam i. At the free end of the rocker arm 6 is a finger 9 that extends to the right and contains in its end an eye in which receives the upper thread I I. Above this finger and parallel to it and extending to the right is another finger I2. Mounted in the wing I3, which extends outward from the face of the rocker arm 5 at the base of the finger I2, is a third finger It also extending to the right. The finger it is removable from the wing-to facilitate replacement, and is secured wit-hinthe wing by means of the screw I 5.

The swingable arm I6, pivoted at the lower left by means of the eccentric stud Il, contains an elongated slot iii in which the face cam roller 4 operates. The eccentric stud is used to adjust the length of the upper thread loop that is drawn into the material. This adjustment is necessary when a different thickness of material is sewn. At the free end of the swingable arm I6 is a finger l9. This finger is removable from the swingable arm it to facilitate replacement and is secured within the swingable arm by means of the screw 23. The movement of the cam guides the rocker arm 6 in a back and forth motion and the swingable arm iii in an up and down motion in suitable timed relation.

The needle 2i contains a heavier portion 38 as indicated in Figures 6 and 60.. As the needle lowers to receive the machine thread 22 this heavier portion enlarges the upper portion of the hole in the material. The enlargement of the hole is necessary to receive the heavy upper por- The needle is shaped as shown in Figures 6 and 6a to achieve the enlarged portion of the hole and still retain a good bearing surface against the needle guide 24 at all positions.

The slack take up device, Figure 3, serves to guide the upper thread it around the corner and also to maintain tension on it throughout the formation of the stitch. This device consists of the roller 25 mounted on the axle 34 in the frame 26 which is pivoted by means of stud 2?. The spring 28 mounted on the stud has a free end bearing against the extension of the axle 34. Mounted on the stud 2? within the frame is another roller 23 which serves as a thread guide. Tension produced on the upper thread I I by the movement to the right of the rocker arm 6 urges As the tension is relieved by the movement of the rocker arm to the left, the spring urges the roller back to the normal position as indicated in Figure 1.

The cover 33 serves to prevent lateral play in the swingable arm. The inner surface of the cover is in slidable contact with the face 23 of the swingable arm.

As the needle 2 i. lowers to pick up the machine thread v22 it enlarges the hole in the upper portion of the work. It then raises the machine thread 22 and in cooperation with the thread lifter 3i spreads the loop in the usual manner. At this time the cam I rotates counterclockwise guiding the rocker arm 6 to the right. The lower finger i. of the rocker arm carries the upper thread loop through the machine thread loop as the rocker arm fingers I2 and I4 pass within the .machine thread loop as shown in Figures 2 and 5. As the rocker arm 6 advances the swingable arm I6 lowers so that the point of the swingable arm finger I8 passes through the upper thread loop. As the swingable arm finger I9 lowers the needle 2I advances slightly and the thread lifter 3I lowers slightly freeing the machine thread 22 of the needle and thread lifter so that the upper part of the swingable arm finger I9 can push the thread 22 out of their paths. When the swingable arm finger I9 reaches the upper surface of the work, indicated by the dotted line, the rocker arm retreats and the point of the swingable arm finger I9 retains the loop of the upper thread through the machine thread as shown in Figure '7. The usual thread tightening means (not shown) come into play and draw the machine thread loop 22 from the rocker arm fingers I2 and I4. The swingable arm finger I9 remains in the lowered position and serves to prevent the machine thread loop from being drawn back onto either the needle 2| or the thread lifter 31., and retains the upper thread loop until the machine thread loop 22 has drawn it part way into the material. The cam I then reverses direction and the swingable arm finger l9 raises as the upper thread loop is completely drawn into the material. The awl 32 then raises and punches a hole in the material and the work is then shifted to the left by the usual means to prepare for another stitch. Then the awl 32 retreats and the needle 2-! advances to enlarge the upper part of the hole and receive the machine thread and the cycle proceeds again as described above.

The cycle of operations is diagrammatically illustrated in Figure 4. Assuming that the start of the cycle is as indicated, the cams are arranged so that the awl advances to punch the hole as the swingable arm raises and the rocker arm retreats from the positions of Figure 2 to the positions of Figure 1. Next the needle operating mechanism functions in the usual manner to lower and raise the needle. After the needle is lowered and raised the thread lifter spreads the machine thread. Then the rocker arm fingers 9, [2 and I4 engage the machine thread as the needle advances slightly and the thread lifter lowers slightly leaving the machine thread loop on the rocker arm fingers I2 and I4. The swingable arm then lowers and theswingable arm finger I9 engages the upper thread loop which has been passed through the machine thread loop by the rocker arm finger 9. 'Then the rocker arm retreats as the swingable arm finger l9 retains the upper thread loop through the machine thread loop. Then the machine thread tightening mechanism acts to pull the upper thread loop within the material. Just as the machine thread loop enters the material the swingable arm finger raises and the upper thread loop is drawn into the material by the machine thread loop, and the stitch is completed.

It is obvious that the invention may be embodied in many forms and constructions in the scope of the claims and I wish .it to be understood that the particular form shown is but one of .the many forms. Various modifications and changes being possible, I do not otherwise limit myself in any way with respect thereto.

What is claimed is:

1. In a loop lock shoe sewing machine; the improvement comprising a needle and looper mechanism acting on a machine thread to pull a loop of thread through the work and spread open said machine thread loop, machine thread loop retaining fingers and means for passing said fingers into the spread machine thread loop, and

upper thread loop carrying finger and means for directing said finger into the spread machine thread loop as the machine thread loop retaining fingers are entering said spread machine thread loop, an upper thread loop retaining finger and means for directing said finger into the upper thread loop after the upper thread carrier has passed said loop through the machine thread loop, mechanism for drawing the machine thread loop upon the retained upper thread loop as the upper thread loop carrying finger and the machine thread loop retaining fingers are withdrawing from the machine thread loop, and means for removing the upper thread loop retaining finger before said loop is drawn fully into the material.

2. In a machine for sewing material such as claimed in claim 1, a sewing machine needle having two ribs opposite each other alongside the body of the needle for enlarging the hole in the upper piece of material to receive the two loops.

3. In a loop lock shoe sewing machine; the improvement comprising a needle and looper mechanism acting on a machine thread to pull a loop of thread through the work and spread open said machine thread loop, machine thread loop retaining fingers and an upper thread loop carrying finger, a reciprocatory common carrier to move the said machine thread loop retaining fingers and upper thread loop carrying finger transversely into and out of the spread machine thread loop, an upper thread loop retaining finger and means for passing said finger into the upper thread loo after the upper thread loop carrying finger has passed said loop through the machine thread loop, a machine thread tightening mechanism for drawing the machine thread loop upon the retained upper thread loop as the upper thread loop carrying finger and the machine thread loop retaining fingers are withdrawing from the machine thread loop, and means for removing the upper thread loop retaining finger before said loop is drawn fully into the material.

4. In a loop lock shoe sewing machine; the improvement, comprising a needle and looper mechanism acting on a machine thread to pull a loop of thread through the work and spread open said machine thread loop, a rocker arm having an upper thread loop carrying finger and machine thread loop retaining fingers, said machine thread loop retaining fingers acting on the spread machine thread loop to free said loop from the needle and looper mechanism and retain said loop while the upper thread loop carrying finger introduces the upper thread loop into the retained machine thread loop, a swingable arm having a loop retaining finger for retaining the upper thread loop through the machine thread loop after the upper thread loop carrying finger has been withdrawn from the machine thread loop; and means for operating the needle and looper mechanism, rocker arm, and swingable arm in proper timed relation.

5. In a loop lock shoe sewing machine, the improvement comprising a needle and looper mechanism acting on a machine thread to pass a 1001) of thread through the material and spread open said machine thread loop, a rocker arm having machine thread loop retaining means for retaining the spread machine thread loop, said rocker arm including an upper thread loop carrying means for passing a loop of the upper thread through the spread machine thread loop, a swingable arm having a finger for retaining the upper thread loop through the machine thread loop after said upper thread loop carrying means has withdrawn from the machine thread loop, means for operatin said rocker arm and swingable arm in timed relation.

6. In a loop lock shoe sewing machine; the improvement comprising a rocker arm having a loop carrying finger containing an eye in the front section thereof, said rocker arm including loop retaining fingers, and means for passing the loop carrying finger and loop retaining fingers into a preformed thread loop that has been passed through the material.

FRANK PRAVDA.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS.

Number Name Date 666,225 Bean Jan. 15, 1901 1,131,853 Myers Mar. 16, 1915 

